[Guna]

Originally Posted by SS-Traveller

Not adequately experienced in driving gizmo-laden 4wd's off-road, so cannot really comment. From what I understand of the Freelander2 / BMW X5/6, these don't use 4L gearing. There are loads of electronics though, and it is said that with loss of traction on 3 wheels (such as putting them on rollers), the electronics can still get the car moving with the help of any one wheel. How that behaves in the real world, I have no exposure to.

Subaru AWD system is also supposed to be capable of moving the car with just one wheel having the traction. I dont think there is much electronics here. They seem to be attributing a lot to the 'symmetrical drive'.

http://www.youtube.com/watch?v=t09ExAUgtyE

[s_pphilip]

Originally Posted by Endeavour333

Endeavour: Part-time 4x4 with Center Transfer case, Torsen LSD in the rear - Meaning that you would need to lose traction in 3 wheels to come to a halt. Even if one rear wheel is in the air you can use the throttle-brake technique to get some power to the rear wheel that has traction to get out.

Fortuner: Lockable center Torsen differential that will just act like a Transfer case once locked, and also the India version of the Fortuner has No LSD in the rear. Meaning that once the center diff is locked, you would need to lose traction in only 2 wheels to come to a halt.

Pajero: Full time and part time 4x4 with a lockable viscous coupling differential in the middle. No limited slip differential in the rear. The 'Super Select 4x4' allows you to switch between the various modes like with center diff locked/unlocked, etc. No fancy electronics other than that. So once again this means that if you lose traction on one rear and one front wheel you're stuck.

If all the above is true then shouldn't the Endeavour possess the best off road hardware?

I'm also pretty certain that the Torsen Differential is considered to be the best sort of LSD right now. So why then is the Pajero considered to be such a good off roader? (just looking at the 4x4 system)

So considering all this, the Endeavour should be considered the best off-roader in theory right?
- Vishnu

I believe the humble Tata Safari 4x4's (all gens) have a center LSD and a rear LSD, though both are not lockable (correct me if wrong). The front is regular Open Diff.
So does that not mean for the Safari to keep moving in Slush or Ice one needs traction/torque at only one of the rear wheels. (correct me again).

In effect is that not quite similar in principle to the Endeavour then, making the Safari equally/more competent than others here?
So unless you are not on boulders & rocks & steep inclines, I think clutch type LSD's are better than Torsens in that they work even when there is less spin or no traction at one wheel, better for slush or ice.
I doubt any of the 10+ lakh Indian SUV's will be subjected to hard terrain/serious off-roading, even with all their proclaimed competence they will be easily beaten by the lighter Mahindra's & Gurkha's & Gypsy's.
Okay, maybe water wadding depth can be the only difference, again its avoided as much.

I am impressed by Gurkha's credentials. Serious machine. I think they are the ones who should start the off road adventure club.
How much of a competent road machine it is, only owners can tell.

This is why:
About Torsen:
"This is a torque sensing differential rather than speed sensing. As such it does not try to make the inside wheel turn same speed as the outside wheel. As long as both wheels have traction it transmits equal torque to both wheels regardless of relative wheel speed, very similar to an open differential. One nice feature here is very little affect on understeer or over steer with throttle changes.
However, if one set of wheels loses traction completely, the Torsen differential will be unable to supply any torque to the other set of wheels."

About Clutch Type LSD:
"Getting back to the situation in which one drive wheel is on the ice and the other one has good traction:
With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move.
The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car.
With enough spring force the one wheel could accept all of the available propshaft torque in the lowest gear, or as much torque as it will take to spin the tire (whichever is less)."

[Sawyer]

Originally Posted by s_pphilip

I believe the humble Tata Safari 4x4's (all gens) have a center LSD and a rear LSD,

No, it doesn't. That is why it gets damaged by even ignorant Tata service techs who run it in 4x4 on tarmac.

[s_pphilip]

Originally Posted by Sawyer

No, it doesn't. That is why it gets damaged by even ignorant Tata service techs who run it in 4x4 on tarmac.

Can you please elaborate what are the technical combinations/drivetrains/differentials offered in the Safari 4x4.
I thought Safari has a LSD in the rear and by default runs in 4x2 mode powering the rear wheels and has shift on fly.

[Sawyer]

No, the 4x4 Safari is just like the Gypsy. Rear and front diffs, no LSD, no centre diff. Gypsy too has shift on the fly, one only needs to come to a halt to engage low range. Both run in rwd mode normally.

[.anshuman]

Originally Posted by Sawyer

No, the 4x4 Safari is just like the Gypsy. Rear and front diffs, no LSD, no centre diff. Gypsy too has shift on the fly, one only needs to come to a halt to engage low range. Both run in rwd mode normally.

Safari 4x4 has Limited Slip Differential at rear axle, since the first gen.

[eq24]

Wow this is like a treasure trove of information. I was wondering the main contributors on this thread are hobbyists or professional engineers. Not that it makes a difference, knowledge is knowledge whatever the source.

One small question, how does one decide which 4WD system to go for. In today's Gurgaon times there is a big article on off reading and it caught my attention. How does one start on the path to selecting which system to use. Bearing in mind at the onset one would be a complete and utter novice so simplicity would be key but as one progresses to advance levels the system should also keep up.

One more thing, I recently sat in a Volvo truck with a crawling feature, is this 4x4 based, would love to have it for Delhi traffic.
Thanks

[Sawyer]

Originally Posted by eq24

One small question, how does one decide which 4WD system to go for. In today's Gurgaon times there is a big article on off reading and it caught my attention. How does one start on the path to selecting which system to use.

First, be clear what you want to do with the car. Off roading - and I did just enough of it in my Gypsy to know what the car can do in case of need - can mean walking ahead of the car to take a look at the terrain, and then come back and drive over it. Seems quite pointless to me, why not just walk all the way?! But, it has its adherents that enjoy this activity immensely.
On the other hand, if you want a car that can do Ladakh and other less travelled to places in India, with poor roads in adverse climates, that is another application.
The car you get, depends on the application you want to use it for.

[.anshuman]

Originally Posted by s_pphilip

Can you please elaborate what are the technical combinations/drivetrains/differentials offered in the Safari 4x4.
I thought Safari has a LSD in the rear and by default runs in 4x2 mode powering the rear wheels and has shift on fly.

Safari 4wd does not come with a center differential, so it lacks full time 4wd/AWD capability. The system is similar to Mahindra Scorpio, only difference is Safari on the rear axle has a LSD, Scorpio comes with a open diff. On road Safari runs in 2wd mode.

Switchable modes are 2H(2wd High), 4H(4 High) and 4L(4 Low).

[nilanjanray]

Originally Posted by SS-Traveller

The query above is not the same as...

Between wheels on the same axle:
TCS makes use of LSD practically redundant. I cannot offhand point to any car that has TCS as well as LSD.

E.g. all the new Toyota 4WD SUVs? Isn't the Toyota 'VSC' system another (proprietary) term for TCS++ e.g. TCS + steering angle sensor, yaw rate sensor etc?

I believe the VSC automatically gets disengaged in 4L, and/or there is a manual option to shut it off when offroading. I have the older Fortuner, so this is not based on first hand experience.

From Toyota's website:

Vehicle Stability Control (VSC)

"VSC 7 helps prevent wheelslip and loss of traction by reducing engine power and applying brake force to wheels that need it. The system reads data from a steering wheel sensor and the ABS wheel-speed sensors to determine if the vehicle is following the driver’s steering inputs. If the vehicle is deviating from the direction in which the driver is steering, VSC is designed to reduce engine power and pulse the left- or right-side brakes to help correct the situation."
Another easy to understand explanation here:

http://www.drivingdynamics.info/ask-...ility-control/

"Traction control electronically controls the spin of each wheel. When one wheel begins to turn faster than the others, it is because that wheel’s grip with the road surface has been compromised in some way, so that it is no longer providing equal traction. To control this, the vehicle’s electronic control unit (ECU), which is the electronic “brain” of the vehicle, triggers the brake for the spinning wheel for an instant to control the spin. The goal is to control traction before it causes a loss of control.
Where traction control deals only with wheel spin, electronic stability control deals with total vehicle control including the wheels, the steering wheel, acceleration and the pitch, or rotation, of the vehicle from side to side. Sensors compare steering input to the actual direction the vehicle is traveling. If there is a difference, the computer can either apply braking to one or more wheels or cut engine power in order to keep the vehicle in control."

[s_pphilip]

Originally Posted by eq24

Wow this is like a treasure trove of information. I was wondering the main contributors on this thread are hobbyists or professional engineers. Not that it makes a difference, knowledge is knowledge whatever the source.

One small question, how does one decide which 4WD system to go for. In today's Gurgaon times there is a big article on off reading and it caught my attention. How does one start on the path to selecting which system to use. Bearing in mind at the onset one would be a complete and utter novice so simplicity would be key but as one progresses to advance levels the system should also keep up.

One more thing, I recently sat in a Volvo truck with a crawling feature, is this 4x4 based, would love to have it for Delhi traffic.
Thanks

Well the interesting thing about making this "which 4x4" decision is, normally most lay people associate 4x4's to just the label on the back of their SUV's without realizing the internal mechanicals, you need to dig in information or be part of technical forums to go beyond the superfluous,
I owe much of my information/interest to T-BHP where people discuss at a deeper level and its not a normal sales talk. Most sales advisers don't know their products well.

As 'Sawyer' rightly said it depends on what you exactly want to do. Like most people, we want our cars to be capable of doing everything, not realizing what we want is not always needed based on our usage, moreover some needs contradict other wants.

4x4 application's is one such easily confused subject and that's where many prospective buyers get carried away.

If you follow this thread closely a lot of your related questions will be answered in due course if not done already.

For instance the 4x4 crawling feature you referred to is used when climbing up/down steep inclines or complex terrain, on normal roads your driving inputs constantly vary due to traffic and other road conditions and you wouldn't want the vehicle to restrict your inputs as the vehicle will be following a different set of parameters.
This way there is more stress and wear and tear on the mechanicals and the efficiency goes for a toss and hence you have to disable some features from a proper 4x4 to use on road to avoid damaging the drivetrain.

A simpler solution that works much better is an automatic, for that matter a Nissan Micra automatic will do better in the city when crawling than all these features you think you need.

If you think you want a 4x4 for touring cross country, a normal FWD will offer better fuel efficiency and higher speeds as 95% of your travel will be on paved roads or you can plan to reach places taking the easier optional route.

If you use a proper 4x4 for everyday regular use, you are not using it to its potential, off roading is totally a fun hobby that you opt for consciously.

Where you can have some brief 4x4 applications is on trips to places like Rajasthan or Leh, again note, to get there you need to travel 90% by normal roads, so you need a comfortable car, which is where the part-time 4x4's or AWD's come in.

So a SUV, example Safari, which is comfortable on road and has some off-roading capabilities is probably what you need. It also has a crawling speed gear.

Example as quoted in my earlier post: "So unless you are not on boulders & rocks & steep inclines, I think clutch type LSD's are better than Torsens in that they work even when there is less spin or no traction at one wheel, better for slush or ice.

I doubt any of the 10+ lakh Indian SUV's will be subjected to hard terrain/serious off-roading, even with all their proclaimed competence they will be easily beaten by the lighter Mahindra's & Gurkha's & Gypsy's."

So it totally depends on what terrain and how much you want to pursue this (expensive relatively) hobby, because heavy off roading, there are chances you will damage something.

I am sure lot more like minded people here will elaborate on this.

[SS-Traveller]

Originally Posted by nilanjanray

E.g. all the new Toyota 4WD SUVs? Isn't the Toyota 'VSC' system another (proprietary) term for TCS++ e.g. TCS + steering angle sensor, yaw rate sensor etc?

Again, not exposed to the Toyota system. But now that you mention it, I seem to recall that the VW (Touareg) and Porsche (Cayenne) systems do have a system to lock both centre diff as well as front and rear diffs when operating in 4L mode - and TCS gets deactivated in 4L mode.

Originally Posted by Sawyer

First, be clear what you want to do with the car.
The car you get, depends on the application you want to use it for.

Originally Posted by s_pphilip

If you use a proper 4x4 for everyday regular use, you are not using it to its potential, off roading is totally a fun hobby that you opt for consciously.
Where you can have some brief 4x4 applications is on trips to places like Rajasthan or Leh, again note, to get there you need to travel 90% by normal roads, so you need a comfortable car, which is where the part-time 4x4's or AWD's come in.

You know what I want a 4wd for? To simply drive on regular highways during my daily commutes, and bring me back home as soon as possible without getting stuck, especially when/after it rains! Here's one such long and boring video (please don't curse me - it's all of 20 minutes long) from the dashcam - edited to make it a little shorter.

[s_pphilip]

Originally Posted by SS-Traveller

..... and TCS gets deactivated in 4L mode.

You know what I want a 4wd for? To simply drive on regular highways during my daily commutes, and bring me back home as soon as possible without getting stuck, especially when/after it rains!

Like I mentioned in agreement earlier, my humble 2 cents after research, similar for AWD's too:
"All-wheel drive AWD vehicles often have an electronically controlled coupling system in the transfer case or transaxle engaged (active part-time AWD), or locked-up tighter (in a true full-time set up driving all wheels with some power all the time) to supply non-slipping wheels with (more) torque.

There are instances when traction control is undesirable, such as trying to get a vehicle unstuck in snow or mud. Allowing one wheel to spin can propel a vehicle forward enough to get it unstuck, whereas both wheels applying a limited amount of power can't get the same effect. Many vehicles have a traction control shut off switch for just such circumstances."

SS-Traveller, that is the best application of a 4x4, and makes everyone want one. Fab application and great thread proving it. :-)

[s_pphilip]

Originally Posted by .anshuman

Safari 4wd does not come with a center differential, so it lacks full time 4wd/AWD capability. The system is similar to Mahindra Scorpio, only difference is Safari on the rear axle has a LSD, Scorpio comes with a open diff. On road Safari runs in 2wd mode.

Switchable modes are 2H(2wd High), 4H(4 High) and 4L(4 Low).

So does that mean we can't use 4H on normal roads, the front being open diff, should not be a problem right?
Also something I want to understand is since none of the competition vehicles offer center LSD's or locked center diff's options, am I correct in assuming that Safari is pretty much on par with other SUV's below 25 lacs in India from hardware POV.
Logic- since its is an open center diff, power will take the path of least resistance, not much difference.

I was going through some online sales brochures of 4x4 vehicles in India and I realized that they don't bother to explain or detail what hardware is used to make their machines competent, these brochures talk about decals and chrome extensions but not technicals, its an irony.
So it is left to such forums to detail their mechanicals.

Some vehicles I know from external inputs, a lay persons breakup of its capabilities:

Tata Safari 4x4: has a 4H and 4L gear, along with shift on fly for 2WD to 4WD, has rear LSD. However I have heard of its lack of power/torque, weight is its drawback, the current motor address's this.

Ford Endeavour: has center diff, rear LSD, and is switchable between 2WD and 4WD. Has 4H and 4L. I assume Endeavor will have poor capabilities off track due to poor articulation and over hangs.

Toyota Fortuner: has center diff, no LSD's in center, back or front. Full-time 4x4, has 4H and 4L gears. I believe Fortuner has among the highest water wading capabilities for an Indian SUV. The power is brutal, but no lockable diff's or LSD's.

Most Hyundai's (eg. old Tucson) I believe are AWD's with constant 90:10 split which depending on electronic inputs go up to 50:50. It has a manual over ride below 25kmph.

Though there are some amazing videos on 'You Tube' posted in Russian showing the capabilities of the Tucson, you get a feeling they were just lucky to get away, they take the Tucson to its limits, difficult to believe it can do so.

Similar for Skoda Yeti too, assume it is AWD with hill decent, which is equal to crawling gear. I believe it will be equally competent as the Tucson if not better.
Similar for the Outlander, Vitara and Captiva, real time front biased AWD's.

Mahindra 4x4's are rear wheel driven and have open differentials in front & rear, like in Bolero's/Scorpio's. Have a 4H & 4L gear.
Mahindra's CJ500's are like the benchmarks in India.

I believe you'd need lockable aftermarket differentials to make it a go anywhere car, has decent articulation.
Also regular Mahindra's (not referring to SUV's - XUV types) vibrate and are noisy once above 100 kmph.

Maruti Gypsy too is similar to Mahindra's in set up. So not very comfortable on road or speed.

I believe CRV is too much of a soft roader with no option to switch to 4x4 manually.
Don't know much about Pajero or any other vehicles above it.

The above information may be incorrect and I expect it will be corrected if so. I still am learning.

[.anshuman]

Originally Posted by s_pphilip

So does that mean we can't use 4H on normal roads, the front being open diff, should not be a problem right?
Also something I want to understand is since none of the competition vehicles offer center LSD's or locked center diff's options, am I correct in assuming that Safari is pretty much on par with other SUV's below 25 lacs in India from hardware POV.
Logic- since its is an open center diff, power will take the path of least resistance, not much difference.

No, in 4H mode SUVs like Safari, Scorpio, Endeavour... cannot be used on dry hard surface which does not allow the tires some slip. The reason is- A locking transfer case is used to split power delivery permanently, these vehicles so not have a center differential.

Now just because some vehicles like Fortuner, Pajero, Pajero sport.... have a center differential which enables them to have an extra mode where the vehicle can be used on roads in 4wd mode. This center differential can be locked for a fixed power split, when locked this center differential acts exactly like the locked transfer case i mentioned in the previous paragraph, for example this mode is called 4HL.

I was going through some online sales brochures of 4x4 vehicles in India and I realized that they don't bother to explain or detail what hardware is used to make their machines competent, these brochures talk about decals and chrome extensions but not technicals, its an irony.
So it is left to such forums to detail their mechanicals.

I agree.

Tata Safari 4x4: has a 4H and 4L gear, along with shift on fly for 2WD to 4WD, has rear LSD. However I have heard of its lack of power/torque, weight is its drawback, the current motor address's this.

Most 4wd SUVs have shift on fly function, it enables the driver to shift to 2H to 4H without coming to a halt(4H to 4HL in Fortuner). Every SUV has the weight disadvantage.

Ford Endeavour: has center diff, rear LSD, and is switchable between 2WD and 4WD. Has 4H and 4L. I assume Endeavor will have poor capabilities off track due to poor articulation and over hangs.

Endy does not have center diff, so it cannot be used 4wd mode on roads. With Solid rear axle at back(though with Leaf springs) Articulation at rear is not an problem compared to competition. The huge length and resulting ramp breakover angles issue are the biggest concerns.

Toyota Fortuner: has center diff, no LSD's in center, back or front. Full-time 4x4, has 4H and 4L gears. I believe Fortuner has among the highest water wading capabilities for an Indian SUV. The power is brutal, but no lockable diff's or LSD's.

Fortuner does not have a 2wd mode. It is permanently in 4wd using center differential which also has a LSD, but both front and rear differentials are open. AFAIK in some markets Fortuner get a lockable rear differential.

Most Hyundai's (eg. old Tucson) I believe are AWD's with constant 90:10 split which depending on electronic inputs go up to 50:50. It has a manual over ride below 25kmph.

Similar for Skoda Yeti too, assume it is AWD with hill decent, which is equal to crawling gear. I believe it will be equally competent as the Tucson if not better.
Similar for the Outlander, Vitara and Captiva, real time front biased AWD's.

I believe CRV is too much of a soft roader with no option to switch to 4x4 manually.

In comparison to the above vehicles Tucson, Santa FE, XUV-500, Outlander etc are not exactly as much off road capable. They all come with a Monocoque chassis, Independent Suspension and AWD systems which make them far better in terms of on road dynamics but offroadign abilities are not as good as the above discussed Ladder Frame Chassis trucks.

Mahindra 4x4's are rear wheel driven and have open differentials in front & rear, like in Bolero's/Scorpio's. Have a 4H & 4L gear.
Mahindra's CJ500's are like the benchmarks in India.

Maruti Gypsy too is similar to Mahindra's in set up. So not very comfortable on road or speed.

Also regular Mahindra's (not referring to SUV's - XUV types) vibrate and are noisy once above 100 kmph.

The system used in these vehicles is similar to vehicle i mentioned in Para#1(Safari/Scorpio..) except most of these use front solid axle and are much lighter in weight and smaller in size which gives them the real edge over SUVs.

Also, their vibrating nature has nothing to do with the kind of 4wd system they used. They vibrate due to their vintage engine and other hardware.

I believe you'd need lockable aftermarket differentials to make it a go anywhere car, has decent articulation.

To make a real go anywhere vehicle a lot of modifications can be done, like Off road biased tires, locking differentials, lift kits, snorkel, Winch, more rugged suspension... the list is endless.

But most of the Off-roaders in our country use open differentials.